Planning for Climate Change Impacts on Shellfish in Wellfleet Harbor

Shellfish play a vital role in the ecology of Wellfleet Harbor and the economy of Wellfleet. Wellfleet is one of the leaders in commercial shellfish production in Massachusetts, producing about 23% of the shellfish landings, worth approximately $4,500,000. However, shellfish are particularly vulnerable to climate change and variability. The National Marine Fisheries Service ranks shellfish as among the most vulnerable of fish stocks in the northeastern US.

The website is intended to support planning in Wellfleet that will address the potential impacts of climate change on shellfish and shellfishing in the near and long terms. The information provided can help to inform the boards and committees responsible for the many activities that impact the harbor and shellfishing in Wellfleet Harbor. This website provides an overview of the climate-related threats to shellfish and commercial shellfishing in Wellfleet Harbor and potential strategies that can be considered by the Town of Wellfleet to prevent and mitigate their impacts.

This website summarizes the information developed by a Working Group on Climate Change impacts on shellfishing in Wellfleet Harbor. The Working Group met from 2013 – 2015 to discuss and learn about the following :

threats to shellfishing in Wellfleet Harbor from climate change

the role of shellfish in mitigating impacts from climate change and other environmental hazards in Wellfleet Harbor

strategies to increase the resilience of Wellfleet and its shellfishery in a time of climate change.

SUPPORTING MATERIALS

Climate Change in the Coastal NE Atlantic

A key finding of a recent assessment is that climate change will exacerbate heat waves, coastal flooding, and river flooding in the northeastern United States. Both air and water temperatures are expected to increase as a result of climate change. Across the continental US precipitation is falling in more intense events. This trend is especially strong in the northeastern US. Some of these heavy precipitation events will be in the form of hurricanes and winter northeasters.

Furthermore, the number and power of severe storms is predicted to increase in the future, even as the overall frequency of storms may decrease. Sea level rise will increase near-shore flooding as well. In addition, ocean chemistry is changing, and the main focus of attention has been ocean acidification, which occurs when increased CO2 uptake reduces available carbonate ions.

Threat – Sea Level Rise

Relative sea levels are predicted to rise from several causes. Sea levels are rising in Wellfleet from a combination of rising ocean waters and land subsidence. An additional factor that may increase sea level rise in the northeastern US compared to other parts of the globe is the slowing of ocean currents. In the northeastern US the combination of rising ocean waters and land subsidence is leading to higher relative sea level rise compared to many other coastlines in the US and elsewhere.

Recent assessments have estimated additional sea level rise along the Massachusetts coast of 8 to 16 inches by 2050 and 20 to 55 inches by 2100.

Threat – Changes in Intensity and Frequency of Heavy Precipitation

Across the continental US precipitation is falling in more intense events. This trend is especially strong in the northeastern US, which has seen a 71% increase in heavy precipitation events from 1958-2012. Heavy precipitation events are expected to double in the Northeast by 2100 and coastal areas have the highest amounts of precipitation within the Northeast region. Seasonal variations are also expected; more winter precipitation will fall as rain, and less as snow; this is due in part to warmer winter air temperatures. Heavy precipitation events are associated with high winds and storm surge. High winds and storm surge can exacerbate coastal erosion and cause damage to infrastructure.

Threat – Increasing Water and Air Temperatures

Both air and water temperatures are expected to increase as a result of climate change. An air temperature increase of 3-10° F in the Northeast by 2080 is possible, but these are annual averages, and the changes are expected to vary across seasons. Most of the warming will be experienced in the winter, rather than summer, months. During the summer heat waves are expected to be more frequent, intense, and prolonged. Sea surface temperatures are also predicted to rise, by up to 4 to 8° F by end of the century.

A recent assessment for Massachusetts reported an average annual sea surface temperature of 53° F in coastal MA waters, which may increase to 55-56° F by 2050 and 57-61° F by 2100.

Threat – Ocean Acidification

Ocean chemistry is changing, and the main focus of attention has been ocean acidification, which occurs when increased CO2 uptake reduces available carbonate ions. Recent projections suggest, under high emission scenarios, that global average pH could decrease from 8.1 to 7.8 by the end of the century. However, there are many factors that will influence local levels of pH, especially in near shore areas.